1. Field of the Invention
This invention relates to an improved transcutaneous electrical nerve stimulation (TENS) apparatus for symptomatic relief and management of chronic (long term) intractable pain and adjunctive treatment in the management of postsurgical traumatic acute pain. More specifically, the invention relates to a TENS device that operates in the electrical current range of about 25 microamps to less than 1 milliamp using a chopped (e.g., 9.125 Hz or 292 Hz) carrier frequency (e.g., 15,000 Hz) having typically a monophasic wave profile which is preferably inverted (reversed polarity) approximately every second.
2. Description of the Prior Art
It is generally known and an accepted practice to administer transcutaneous energy in the form of light and/or electrical current as a therapeutic treatment particularly to alleviate certain types of pain. Such treatments are frequently compared to acupuncture both in terms of application and results. It is also generally known in both types of transcutaneous radiation therapy that the body will favorably respond to certain preselected discrete beat frequencies. Thus for example in U.S. Pat. No. 4,232,678; 4,553,546 and 4,646,743 and French patent No. 2371935 various types of infrared (IR) and/or near IR light sources are chopped (modulated on and off in time) at selected frequencies to produce a pulsating source of IR radiation as a transcutaneous energy to be applied to mammalian tissue. Analogously, U.S. Pat. Nos. 3,785,383 and 3,902,502 disclose a transcutaneously applied capacitively coupled electrostatic electrode system and a microcurrent conductivity coupled electrode system, respectively, for the purpose of reducing sensitivity to pain. In the later disclosure the concept of modulating the carrier frequency by superimposing a beat frequency is employed. Instruments specifically designed to accomplish this type of electric current therapy are now commonly referred to as transcutaneous electrical nerve stimulators (TENS).